Deck 12: Electrophysiology of the Heart

Question 1

What is the term for the unique ability of cells in the SA node to generate an action potential without being stimulated?

A) automaticity
B) excitability
C) contractility
D) conductivity

Answer 1

A

Question 2

Which phase of the action potential prolongs the contraction of the myocardial cells?

A) Phase 2
B) Phase 3
C) Phase 4
D) Phase 5

Answer 2

A

Question 3

What is the term for the time in which cells cannot respond to a stimulus?

A) absolute refractory period
B) relative refractory period
C) nonrefractory period
D) partial resistance period

Answer 3

A

Question 4

What is the term for the ability of the heart cells to transmit electrical current from cell to cell?

A) conductivity
B) contractility
C) automaticity
D) irritability

Question 5

Of the phases of the action potential, which phase represents rapid depolarization of the myocardial cells?

A) Phase 0
B) Phase 1
C) Phase 4
D) Phase 5

Question 6

What is the term for the ability of cardiac muscle fibers to shorten in response to an electrical stimulus?

A) contractility
B) conductivity
C) automaticity
D) excitability

Question 7

What is the term for the ability of a cell to reach its threshold potential and respond to a stimulus?

A) excitability
B) conductivity
C) contractility
D) automaticity

Question 8

At the end of Phase 0,what does the voltage inside the myocardial cell equal?

A) +30 mV
B) +15 mV
C) -30 mV
D) -90 mV

Question 9

Which phases of the action potential represent the absolute refractory period?
I)Phase 0
II)Phase 1
III)Phase 2
IV)First half of Phase 3
V)First half of Phase 4

A) I, II, III, and IV only
B) I, II, and III only
C) IV and V only
D) II, III, and IV only

Question 10

After the electrical impulse leaves the atrioventricular junction,where does it travel next?

A) bundle of His
B) bundle branches
C) Purkinje fibers
D) Bachmann's bundle

Question 11

What is the basic term for the phase in which the heart is not generating an action potential?

A) polarized
B) depolarized
C) contractile
D) conductive

Question 12

Which portion of the conductive system is considered to be the pacemaker of the heart?

A) sinoatrial node
B) sinoarterial node
C) atrioventricular node
D) arteriovalvular node

Question 13

Which phase of the action potential represents the relative refractory period?

A) Last half of Phase 3
B) First half of Phase 3
C) Last half of Phase 4
D) First half of Phase 4

Question 14

Approximately what percentage of the heart is composed of autorhythmic cells?

A) 1%
B) 12%
C) 18%
D) 24%

Question 15

What are the three promary electrolytes responsible for the electrical difference across the resting membrane potential?

A) potassium, sodium, and calcium
B) potassium sodiun, and chloride
C) sodium, chloride, and bicarbonate
D) sodium, chloride, and potassium

Question 16

Which phase of the action potential represents initial repolarization of hte myocardial cells?

A) Phase 1
B) Phase 2
C) Phase 3
D) Phase 0

Question 17

What does the RMP of the myocardial cells equal?

A) -90 mV
B) -50 mV
C) -30 mV
D) -15 mV

Question 18

Which phase of the action potential represents the nonrefractory period?

A) Phase 4
B) last half of Phase 3
C) first half of Phase 3
D) Phase 5

Question 19

During which phase of the action potential do the voltage-sensitive ion channels return to their pre-depolarization permeability?

A) Phase 4
B) Phase 3
C) Phase 5
D) Phase 0

Question 20

What is the term for the electrical currents that travel across the cell membranes of the heart?

A) action potential
B) nerve impulse
C) stimulus
D) conduction

Question 21

Where does the electrical impulse travel after leaving the AV bundle?

A) left and right bundle branches
B) bundle of His
C) Purkinje fibers
D) SA node

Question 22

In a healthy adult at rest,approximately how much time is required for the entire heart to depolarize?

A) 0.22 seconds
B) 0.02 seconds
C) 2.2 seconds
D) 0.002 seconds

Question 23

What are indications for synchronized cardioversion?
I)Unstable atrial fibrillation
II)Atrial flutter
III)Atrial Tachycardia
IV)ventricular fibrillation

A) I, II, and III only
B) I, II, II, and IV only
C) IV only
D) I and III only

Question 24

At what point do the internodal tracts of the right atrium merge?

A) AV junction
B) SA junction
C) Bachmann's bundle
D) Purkinje fibers

Question 25

What effect does stimulation of the parasympathetic neural fibers have on the contactility and AV conduction of the heart?

A) Both contractility and AV conduction would decrease
B) Both contractility and AV conduction would increase
C) Contractility would increase and AV conduction would decrease
D) AV conduction would decrease and contractility would not be affected

Question 26

What effect will stimulation of sympathetic neural fibers have on heart rate and excitability?

A) both will be increased
B) both will be decreased
C) heart rate will increase and excitability will decrease
D) heart rate will increase and excitability will be unaffected

Question 27

Which structure transmits the electrical impulse from the SA node to the left atrium?

A) Bachmann's bundle
B) AV junction
C) bundle of His
D) Purkinje fibers